"We found with this study that the internal circadian system also likely plays a role in today's obesity epidemic," says Shea, "because it intensifies hunger at night."

Shea and colleagues sequestered a dozen healthy, non-obese adults in a laboratory for 13 days, spacing their meals and activities evenly across the day and night in order to examine the true internal circadian effects on appetite. Participants felt least hungry in the morning and most hungry in the evening, especially for sweet, starchy, salty foods.

Trouble is, the body typically doesn't expend as much energy after an evening meal as after a morning meal. It stores it instead, often in the places you least want it, like your thighs or belly.

"Knowing how the body operates will help you make better choices," Shea says in an OHSU news release. "Going to bed earlier, getting enough sleep and choosing lower-calorie foods rather than higher-calorie foods in the evening can all help with weight loss."